1. Field of Invention
The invention relates to an internal combustion engine and more particularly, to a lubricating oil passage in the internal combustion engine.
2. Description of Related Art
In an internal combustion engine, a cam driven valve has been generally employed for an intake valve and an exhaust valve. Recently, an electromagnetically driven valve has been employed as the intake valve or the exhaust valve in place of the cam driven valve. For example, JP-A-11-36829 discloses a full cam-less structure in which the electromagnetically driven valve is employed as both the intake and the exhaust valves, and lubricating oil is supplied to a portion that slides along with the opening/closing operation of the valve body. JP-A-2001-355417 also discloses the electromagnetically driven valve employed in the internal combustion engine.
The lubricating oil for the intake/exhaust valves is generally supplied from a lubricating oil supply system that supplies the lubricating oil to an engine body such as a piston rod within the cylinder block. If the electromagnetically driven valve is employed in the above-structured internal combustion engine, the drawback may occur as described below.
Required properties of the lubricating oil for the electromagnetically driven valve should be different from those of the lubricating oil supplied to a body of an engine. Accordingly, the common use of the lubricating oil both for the electromagnetically driven valve and the engine body may cause any one of them to be brought into the inappropriate state with respect to its performance. The lubricating oil for the engine body is likely to be degraded under the influence of an operation state of the engine. It is, therefore, not appropriate to use the lubricating oil that has been supplied to the engine body for lubricating the electromagnetically driven valve. In the aforementioned case, that is, the degraded lubricating oil is supplied to the electromagnetically driven valve, it may perform its function inappropriately, thus causing the engine to stop, increasing the power consumption, failing to start the engine at low temperatures, and the like.
JP-A-11-36829 discloses the lubricating oil supply mechanism for supplying the lubricating oil to the portion that slides along with the opening/closing operation of the body of the electromagnetically driven valve in the full cam-less structure. The lubricating oil supply mechanism allows the lubricating oil to be supplied only to the electromagnetically driven valve independently from the supply of the lubricating oil to the engine body.
Meanwhile, in an internal combustion engine with the half cam-less structure having the electromagnetically driven valve as one of the intake or the exhaust valves, and the cam driven valve as the other valve. The above-structured internal combustion engine provides advantageous features of the cost reduction, being substantially equivalent to the fuel efficiency obtained in the full cam-less structure. However, it is necessary to consider the system for supplying two types of the lubricating oil to the cam driven valve and the electromagnetically driven valve as being the intake and the exhaust valves. There is disclosed no lubricating oil supply system employed in the internal combustion engine having the lubricating oil supply device with the half cam-less structure.